The third Generation Partnership Project (3GPP) is considering a number of possible control channel (CC) types in the OFDM downlink (DL) of the LTE system. These include DL and UL scheduling, Random Access response, Paging scheduling, Acknowledgement for UL packet, Overload indicator and Category size. At each sub-frame, the system can transmit control information to one or multiple User Equipment (UE). For each UE, one or several CC types can be transmitted.
3GPP also has agreed to a number of main requirements for the transmission of control channels in OFDM communication systems. These include individually encoding and transmitting each control channel type in the first L OFDM symbols of a sub-frame (1≦L≦3 and L may change between sub-frame depending on requirement on number of scheduled UE per sub-frame and/or coverage), frequency-division multiplexing of transmissions between control channels, distributing transmission of each control channel over entire system bandwidth, transmitting each control channel information at different code rates depending on the long term signal-to-noise ratio at User Equipment (UE), performing power control for each CC according to short term signal-to-noise ratio at UE, randomizing inter cell interference for each CC, and using higher layer signaling to inform UE about the configuration (transport format and physical mapping) of each control channel to be monitored.
However, a number of important features relating to the transmission of control channels in OFDM communication systems have yet to be defined. For example, it is not clear yet how many types of control channels are to be supported in current and future long-term-evolution (LTE) systems, and how to provide a simple and future-proof system design to effectively handle the transmission of various types of control channels.
There currently exists a need to provide a simple and unifying technique for transmitting different types of control channels in the downlink of LTE systems whilst still meeting existing 3GPP requirements. There also exists a need to provide for the transmission of control channels in the downlink of an OFDM communication system that ameliorates or overcomes one or more disadvantages, problems or inadequacies of existing OFDM communication systems.